It is known to arrange a diversion device in the cooling air spiral for supplying combustion air to the engine. This diversion device can also be referred to as a pre-separator. The air outlet window of the diversion device is shielded from the fan wheel via a guide wall, so that the air outlet window is for the most part in the flow shadow of the feeding fan wheel. The cooling air flowing to the combustion engine via the air outlet window is sucked in by the combustion engine via the air outlet window as combustion air. Because of the arrangement and position of the window, the combustion air flow is largely free from dirt particles and dust.
The cooling air blower with cooling air spiral and fan wheel is configured to sufficiently cool the combustion engine under a continuous load. Because the diversion device or pre-separator device is located in the cooling air spiral, the form and size thereof must be so configured that the cooling air flow itself is disrupted as little as possible so that sufficient cooling of the combustion engine is ensured in every operating state.
On the other hand, the diversion device or pre-separator is configured such that a sufficient volume of combustion air flows to the combustion engine. A diversion device, matched to the desired dynamic pressure and the desired amount of combustion air supplied, can, however, lead to a significant disruption of the cooling air spiral and the cooling air flow so that the sufficient cooling of the combustion engine is jeopardized.